1. Field of the Invention
The present invention relates to a stereoscopic display apparatus for performing a stereoscopic display on a television system, computer monitor, game machine, and the like, and a screen control method in the apparatus.
2. Related Background Art
As a conventional stereoscopic display method, a method in which images for the right and left eyes are set in different polarization states, and the right and left images are separated using polarization spectacles is known. In order to set different polarization states in this method, a liquid crystal shutter is provided to a display, and the polarization state is switched in synchronism with the field signal of an image displayed on the display, so that an observer who wears the polarization spectacles can watch a stereoscopic view by time-divisional separation of the right and left images for the respective eyes. However, in this method, the observer must always wear the polarization spectacles.
In contrast to this, as a stereoscopic display method which does not use any polarization spectacles, a method in which a lenticular lens is arranged on the front surface of the display, and images to be input to the right and left eyes are spatially separated is known. FIG. 11 is an explanatory view of the conventional method using a lenticular lens. A liquid crystal display 1 comprises a liquid crystal display pixel portion 3 formed between glass substrates 2 and 4. A lenticular lens 5 is arranged on the surface of the liquid crystal display 1. The lenticular lens 5 is constituted by cylindrical lenses each of which has a semi-circular section and extends in a direction perpendicular to the plane of the drawing of FIG. 11. The liquid crystal display pixel portion 3 is located on the focal plane of the lenticular lens 5.
As shown in FIG. 11, pairs of stripe image portions for the right eye (black portions) and the left eye (white portions), each pair of which corresponds to one pitch of the lenticular lens, are alternately arranged on the display pixel portion 3. These stripe image portions are optically separated and imaged by the lenticular lens 5 on right and left eyes E.sub.R and E.sub.L of an observer, thus allowing a stereoscopic view. FIG. 11 illustrates spatial areas, where the images for the right and left eyes can be observed, at the two ends and the central portion of the display. A common area where the eyes (the distance between the centers of the two eyes is e) of the observer can observe the separated right and left images over the entire screen corresponds to a stereoscopic view area 6 indicated by bold lines in FIG. 11. Furthermore, in areas (not shown) adjacent to the stereoscopic view area 6, the observer can stereoscopically observe separated right and left images.
However, the width of the stereoscopic view area is small, and the stereoscopic view range for the observer has a width as small as the distance between the centers of the two eyes, i.e., about 65 mm. For this reason, the observer must fix his or her head position during observation, resulting in uncomfortable observation.
In order to solve this problem, Japanese Laid-Open Patent Application No. 2-44995 has proposed a method of widening the stereoscopic view area by detecting the positions of the two eyes of an observer, and performing movement control of the relative position between a lenticular lens, which is movably supported in the horizontal direction, and display elements on the basis of the detected eye positions. On the other hand, Japanese Laid-Open Patent Application No. 2-50145 has proposed a method of widening the stereoscopic view area by detecting the positions of the two eyes of an observer, and replacing the horizontal positions of display pixel portions of images for the right and left eyes corresponding to the lenticular lens on the basis of the detection signals.
However, in the method of performing movement control of the relative position between the lenticular lens and the display elements, the lenticular lens must be translated without being inclined, while maintaining the focal length to the display elements. In this case, the thin lenticular lens plate is deformed, and it is difficult to maintain an equal distance to the display elements, thus deteriorating an image. Also, high-precision drive and guide/support mechanisms are required, resulting in an expensive apparatus. On the other hand, in the method of replacing the horizontal display positions of images for the right and left eyes, since a black stripe is present between two adjacent display elements, when the two eyes of an observer are just located at the switching positions, the observer undesirably observes the black stripe, resulting in a discontinuous observation. Also, when the switching timing is shifted even slightly, the right and left images are reversed, thus disturbing a stereoscopic view.
In general, in the above-mentioned display method using a lenticular lens, images picked up by stereoscopic cameras or VTRs are directly displayed as images for the right and left eyes to be displayed, and object images in the two images have a predetermined parallax amount on the screen depending on their distances from the cameras. Upon observation, an observer recognizes the depth of an image depending on the parallax amount of object images in the images for the right and left eyes. In this case, when the parallax amount of the object images is larger than the distance which allows the observer to observe the object images as a single image, the object image is doubled, resulting in a difficult observation.